Flood Potential Outlook
Issued by NWS Bismarck, ND

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FGUS73 KBIS 291848
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NDC001-007-011-015-021-025-029-031-033-037-041-043-045-047-051-
053-055-057-059-065-083-085-087-089-093-103-105-312200-

PROBABILISTIC HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE BISMARCK ND
147 PM CDT FRI MAY 29 2015

...Flood and Water Resources Outlook...

This probablistic flood outlook is for the Missouri and James River
basins of North Dakota and covers the period of early June through
late August.

The following message has four sections. The first provides some text
on the highlights of this outlook and conditions affecting the local
hydrology. The second section gives the current and normal/historical
risks of flooding as determined by the Ensemble Streamflow Forecast
model of the National Weather Service. The third section gives the
current probabilities for reaching flood stage at the listed forecast
locations. And finally, the fourth section covers the risk of the
river sites falling below the listed stages.

...Flood Outlook Highlights...
In general, risks presented below tend to reflect a seasonally
normal probability of widespread flooding. This generally should be
interpreted as a relatively low risk of problematic high water. As
the region is now firmly in the summer season, localized
thunderstorms with low to moderate spatial coverage tends to present
the majority of the flood risk and is more of a problem along the
small drainages and ungaged streams than the major rivers.

...Current Conditions...
After the past couple of fairly wet weeks, most rivers and streams
tend to have near normal streamflow for this time of year.
Reservoirs, with the exception of Lake Sakakawea are near their full
supply level and have their full flood storage available for use.
Soil moisture levels have rebounded after being depleted during a
very dry April and early May.



...Weather Outlook...
The near term 6-10 and 8-14 day outlooks generally reflect an
enhanced risk of above normal temperatures and above normal
precipitation. Out past then, the one-month and three-month outlooks
suggest the region has an equal chance for below normal, near normal,
or above normal temperatures and precipitation.


In Table 1 below...the current (CS) and historical (HS) or normal
probabilities of exceeding minor...moderate...and major flood stages
are listed for the valid time period.

CS values indicate the probability of reaching a flood category
based on current conditions.

HS values indicate the probability of reaching of the model
predicting a rise to flood category based on historical or normal
conditions.

When the value of CS is more than HS...the probability of
exceeding that level is higher than normal. When the value of CS is
less than HS...the probability of exceeding that level is lower than
normal.

...Table 1--Probabilities for minor...moderate and major flooding...
                    Valid Period:  05/30/2015  - 08/28/2015

                                       :    Current and Historical
                                       :     Chances of Exceeding
                                       :       Flood Categories
                                       :      as a Percentage (%)
                      Categorical      :
                   Flood Stages (FT)   :   Minor    Moderate   Major
Location           Minor   Mod   Major :  CS   HS   CS   HS   CS   HS
--------           -----  -----  ----- : ---  ---  ---  ---  ---  ---
:Pipestem Creek
Pingree             11.0   13.0   15.0 :  <5   <5   <5   <5   <5   <5
:James River
Grace City          12.0   14.0   15.0 :  <5   <5   <5   <5   <5   <5
Lamoure             14.0   16.0   18.0 :   9    9    6   <5   <5   <5
:Cannonball River
Regent              22.0   24.0   26.0 :  <5   <5   <5   <5   <5   <5
:Cedar Creek
Raleigh             12.0   14.0   16.0 :  <5   <5   <5   <5   <5   <5
:Cannonball River
Breien              10.0   20.0   23.0 :   8   17   <5   <5   <5   <5
:Beaver Creek
Linton              12.0   14.0   16.0 :  22   20    8    9    7    7
:Little Muddy River
Williston           10.0   12.0   14.0 :  25   26   12   23   <5    6
:Little Missouri
Marmarth            18.0   23.0   30.0 :  <5   <5   <5   <5   <5   <5
:Little Missouri River
Medora              15.0   18.0   20.0 :  <5   <5   <5   <5   <5   <5
Watford City        20.0   24.0   30.0 :  <5   <5   <5   <5   <5   <5
:Knife River
Manning             15.0   17.0   20.0 :   8   12   <5   <5   <5   <5
:Spring Creek
Zap                 14.0   18.0   20.0 :  10   11    6    8   <5   <5
:Knife River
Hazen               21.0   24.0   25.0 :   8   10   <5    5   <5   <5
:Heart River
Mandan              17.0   23.0   28.0 :   6    6   <5   <5   <5   <5
:Apple Creek
Menoken             15.0   16.0   17.0 :  25   35   22   26   10   21

Legend
CS = Conditional Simulation (Current Outlook)
HS = Historical Simulation
FT = Feet

In Table 2 below...the 95 through 5 percent columns indicate the
probability of exceeding the listed stage levels (FT) for the valid
time period.

...Table 2--Exceedance Probabilities...

                               Chance of Exceeding Stages
                                  at Specific Locations
                          Valid Period: 05/30/2015  - 08/28/2015
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Pipestem Creek
Pingree               5.1    5.1    5.1    5.3    6.3    8.9   10.6
:James River
Grace City            4.5    4.5    4.5    4.5    6.1    8.6   11.5
Lamoure               7.9    7.9    7.9    7.9    8.9   12.5   16.9
:Cannonball River
Regent                5.3    5.3    5.5    6.6    7.7   10.1   12.4
:Cedar Creek
Raleigh               2.5    2.5    2.9    4.4    5.5    6.7    7.5
:Cannonball River
Breien                4.1    4.1    5.5    7.1    8.3    9.8   10.8
:Beaver Creek
Linton                5.2    5.2    5.6    7.7   11.4   13.2   18.2
:Little Muddy River
Williston             4.7    4.7    4.7    5.1    9.9   12.5   13.6
:Little Missouri
Marmarth              1.4    1.4    1.4    2.1    4.2    6.5   10.9
:Little Missouri River
Medora                2.2    2.2    2.2    3.4    5.5    7.7   11.6
Watford City         -0.1   -0.1    0.1    1.3    3.2    4.9    7.6
:Knife River
Manning               6.5    6.5    6.5    6.7   10.4   14.0   16.0
:Spring Creek
Zap                   5.2    5.2    5.6    6.4   10.9   14.0   19.0
:Knife River
Hazen                 1.8    1.9    3.3    6.2   17.1   20.7   22.1
:Heart River
Mandan                0.5    0.6    2.5    3.9    5.8   10.1   20.6
:Apple Creek
Menoken               7.0    7.0    7.0    9.1   14.8   17.0   18.8

In Table 3 below...the 95 through 5 percent columns indicate the
probability of falling below the listed stage levels (FT) for the
valid time period.

...Table 3--Nonexceedance Probabilities...

                            Chance of Falling Below Stages
                                 at Specific Locations
                          Valid Period: 05/30/2015  - 08/28/2015
Location              95%    90%    75%    50%    25%    10%     5%
--------            ------ ------ ------ ------ ------ ------ ------
:Pipestem Creek
Pingree               5.0    4.9    4.9    4.9    4.9    4.9    4.9
:James River
Grace City            4.2    4.2    4.1    4.1    4.1    4.1    4.1
Lamoure               7.7    7.6    7.4    7.2    7.0    7.0    7.0
:Cannonball River
Regent                5.2    5.2    5.2    5.2    5.2    5.2    5.2
:Cedar Creek
Raleigh               1.2    1.2    1.1    1.1    1.0    0.4    0.3
:Cannonball River
Breien                2.4    2.3    2.1    2.0    1.9    1.7    1.7
:Beaver Creek
Linton                4.6    4.5    4.3    4.2    4.2    4.2    4.2
:Little Muddy River
Williston             4.7    4.7    4.6    4.6    4.5    4.5    4.5
:Little Missouri
Marmarth              1.3    1.3    1.2    1.2    1.2    1.2    1.2
:Little Missouri River
Medora                2.0    2.0    1.9    1.9    1.8    1.8    1.8
Watford City         -0.2   -0.3   -0.4   -0.6   -0.7   -0.9   -1.0
:Knife River
Manning               6.5    6.4    6.4    6.4    6.4    6.4    6.4
:Spring Creek
Zap                   5.1    5.1    5.1    5.1    5.1    5.1    5.1
:Knife River
Hazen                 1.6    1.5    1.4    1.3    1.3    1.2    1.2
:Heart River
Mandan               -0.2   -0.6   -0.7   -0.9   -1.2   -1.5   -1.6
:Apple Creek
Menoken               5.0    4.8    4.4    4.2    4.1    4.1    4.1

These long-range probabilistic outlooks contain forecast values that
are calculated using multiple season scenarios from 30 or more years
of climatological data...including current conditions of the
river...soil moisture...snow cover...and 30 to 90 day long-range
outlooks of temperature and precipitation. By providing a range of
probabilities...the level of risk associated with long-range planning
decisions can be determined. These probabilistic forecasts are part
of the National Weather Service`s advanced hydrologic prediction
service.

Visit our web site weather.gov/bis for more weather and water
information.

The next outlook will be issued toward the end of next month.

$$



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